Multidimensional Compliant Thermal Cap for an Electronic Device

ABSTRACT

A method for fabricating a thermal cap for cooling an electronic device includes steps of: machining a main housing of the thermal cap from a single element of a thermally conducting material; and fabricating a top plate including a centered intact area within the main housing by machining orifices around a perimeter of the main housing. The orifices represent a gap between the top plate and the main housing to allow movement of the top plate in the x, y, and z directions. Additionally, moveable connectors are fabricated along an edge of the top plate by cutting connector orifices in the main housing to allow movement of the top plate in the x direction; and moveable bars coupled with the moveable connectors are fabricated by cutting slot orifices in the main housing to allow movement of the top plate in the y and z directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of co-pending U.S. patent application Ser. No. 10/944,979. The aforementioned U.S. patent application is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED-RESEARCH OR DEVELOPMENT

None.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

None.

FIELD OF THE INVENTION

The invention disclosed broadly relates to the field of electronic devices and more particularly relates to the field of multi-dimensional compliant thermal caps for electronic devices.

BACKGROUND OF THE INVENTION

During the normal operation of a computer, integrated circuit devices generate significant amounts of heat. This heat must be continuously removed, or the integrated circuit device may overheat, resulting in damage to the device and/or a reduction in operating performance. Cooling devices, such as heat sinks, have been used in conjunction with integrated circuit devices in order to avoid such overheating. Generally, a passive heat sink in combination with a system fan has provided a relatively cost-effective cooling solution. In recent years, however, the power of integrated circuit devices has increased exponentially, resulting in a significant increase in the amount of heat generated by these devices, thereby making it extremely difficult to extract heat from these devices.

Heat is typically extracted by coupling a heat spreader and a thermal cap to the electronic device as a heat sink. Heat sinks operate by conducting heat from a processor to the heat sink and then radiating it into the air. The better the transfer of heat between the two surfaces (the processor and the heat sink metal) the better the cooling. Some processors come with heat sinks glued to them directly, or are interfaced through a thin and soft layer of thermal grease, ensuring a good transfer of heat between the processor and the heat sink. The thermal paste serves not only to transfer heat but to provide some degree of mechanical compliance to compensate for dimensional changes driven by the high operating temperatures of the devices. However, the paste is a weak link in the thermal path. Attempts to thin this layer have resulted in failure of the layer when it is exposed to dimensional changes.

There are some known mechanically complaint solutions but these solutions still rely on paste film somewhere in the path. Thus there is a need for a solution that addresses these shortcomings.

SUMMARY OF THE INVENTION

Briefly, according to an embodiment of the invention, a method for manufacturing a cooling structure for an electronic device includes steps or acts of: placing an electronic device on a substrate and producing a cooling structure disposed over the electronic device. The cooling structure includes a plate comprising a thermally conducting material, a first support connected to the plate and a second support connected to the first support, wherein one of the first support and the second support provides compliance in the x-y directions, and the other provides compliance in the z direction.

In yet another embodiment of the present invention, a cooling structure for a plurality of electronic devices comprises a plate for each of the plurality of electronic devices, each plate comprising a thermally conducting material disposed over the corresponding electronic device. The cooling structure further comprises a first support connected to each of the plates and a second support connected to each of the first supports. One of the first supports and the second supports provide compliance in the x-y directions, and the other provides compliance in the z direction.

Further, in another embodiment of the present invention, a method for fabricating a thermal cap for cooling an electronic device includes steps of: machining a main housing of the thermal cap from a single element of a thermally conducting material; and fabricating a top plate including a large intact area within the main housing by machining orifices around a perimeter of the main housing. The orifices represent a gap between the top plate and the main housing to allow movement of the top plate in the x, y, and z directions. Additionally, moveable connectors are fabricated along an edge of the top plate by cutting connector orifices in the main housing to allow movement of the top plate in the x direction; and moveable bars coupled with the moveable connectors are fabricated by cutting slot orifices in the main housing to allow movement of the top plate in the y and z directions.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and also the advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings. Additionally, the left-most digit of a reference number identifies the drawing in which the reference number first appears.

FIG. 1 shows a top view of a multi-dimensional compliant thermal cap disposed over an electronic device, according to an embodiment of the invention;

FIG. 2A shows a side cross-section of a portion of the multi-dimensional compliant thermal cap 100 of FIG. 1;

FIG. 2B shows another side cross-section of a portion of the multi-dimensional compliant thermal cap of FIG. 1, as it adapts to dimensional changes of the electronic device and surrounding structures;

FIG. 3 shows a top view of an alternative multi-dimensional compliant thermal cap, in one embodiment of the present invention; and

FIG. 4 shows a top view of an alternative multi-processor multi-dimensional compliant thermal cap, in one embodiment of the present invention.

DETAILED DESCRIPTION

We describe an apparatus for cooling an electronic device and a method for fabricating the apparatus. FIG. 1 shows a top view of a multi-dimensional compliant thermal cap 100 disposed over an electronic device 104, according to an embodiment of the invention. A compliant thermal cap 100 comprises a moveable top plate 102 for providing the resilience required to overcome the problems of the prior art. The top plate 102 comprises a flat rectangular plate that covers the top surface area of the electronic device (e.g., a semiconductor chip) that is not shown. Note that while a flat plate is preferred, the plate may include a structure, such as heat sink fins, on the side opposing the electronic device. A main housing 110 encircles and is coupled with the top plate 102. The main housing 110 extends downward and is placed on a substrate or an electronic circuit board.

The top plate 102 is attached to at least one movable connector 106 that allows movement of the top plate 102 in the z-directions, or upwards and downwards. In an embodiment of the present invention, the top plate 102 can be connected to additional movable connectors, such as connectors 107, 108 and 109, located in each corner of the top plate 102. The movable connector 106 is further connected to a movable bar 126 that allows movement in the x-y direction, or sideways. Thus, one end of the movable connector 106 is coupled with the top plate 102 and the other end of the movable connector 106 is coupled with the movable bar 126. Note that the movable bar 126 is integrated with the main housing 110 and the movable bar 126 is formed from the establishment of a slot orifice 136. That is, the fabrication of the slot orifice 136 creates the movable bar 126 as an integrated element of main housing 110. In an embodiment of the present invention, additional movable connectors 107, 108 and 109 are connected to additional movable bars 127, 128 and 129, respectively, also allowing movement in the x-y direction. Note that movable connectors 127, 128 and 129 are integrated with the main housing 110 and each movable connector is formed from the establishment of slot orifices 137, 138 and 139, respectively.

Each movable bar 126-129 comprises a thin bar-like structure that can bend or otherwise change shape so as to allow the body of the movable bar to move towards and away from the top plate 102. This bending or morphing action is a result of the spring-like structure of the movable bars. This allows movement of the top plate 102 in the x-y direction, since the top plate 102 is connected to the movable bar 126 or movable bars 126-129.

FIG. 1 also shows orifices 146, 147, 148 and 149. These orifices represent a gap between the top plate 102 and the main housing 110. The orifices 146-149 allow for the movement of the top plate 102 in any direction, including the x-direction and the x-y direction. In an embodiment of the present invention, the orifices 146-149, as well as orifices 136-139, are filled with low-modulus seal material such as silicone. The seal material fills each orifice and allows for stretch and movement in multiple directions such that the thermal compliant cap 100 is compliant with thermal expansion and compression of the electronic device. The seal material can be used to seal the electronic device such that it is environmentally separated from the outside. This can be beneficial in situations where the electronic device can react adversely to air, certain gases, liquids or other environmental hazards.

The compliant thermal cap 100 serves the function of dissipating heat generated by the electronic device and conforms to thermal expansion of the device caused by the difference in the coefficients of thermal expansions of the materials of the device and the top plate 102 of the thermal compliant cap 100 as well as thermally induced dimensional changes in the substrate structure underlying the electronic device. Due to the movable nature of the connectors 106-109 and the bars 126-129, the complaint thermal cap 100 exhibits compliance in multiple directions, specifically, the “z” direction, as well as the “x-y’ directions, i.e., the up, down and sideways directions. Line 150 indicates the plane through which the cross section view of FIG. 2 is taken.

FIG. 2A shows a side cross-section of a portion of the multi-dimensional compliant thermal cap 100 of FIG. 1. FIG. 2A shows the thermal compliant cap 100 and the device 104 in a rest state exhibiting no stress or thermal expansion. The top plate 102 comprises a flat rectangular plate that covers the top surface area of the electronic device 104 (e.g., a semiconductor chip). A main housing 110 encompasses the device 104 and extends downward and is placed on a substrate 120 or an electronic circuit board. FIG. 2A shows the top plate 102 attached to the movable bar 126 via the connector 106. Orifice 136 separates the movable bar 126 from the remaining portions of the main housing 110. In an embodiment of the present invention, a low modulus seal material fills the orifice 136 to provide a seal over the gap.

FIG. 2B shows another side cross-section of a portion of the multi-dimensional compliant thermal cap of FIG. 1, as it adapts to dimensional changes of the electronic device. FIG. 2B shows that the top plate 102 at a greater elevation than the top plate of FIG. 2A. FIG. 2B shows that the electronic device 104 has also increased in vertical size. The increase in vertical size of the electronic device 104 is due to the thermal expansion of the electronic device 104, resulting in the increase in elevation of the top plate 102, which rests on the electronic device 104.

Note that the movable connector 106 has bent to allow the top plate 102 to elevate itself to accommodate the increased size of the electronic device 104. The movable connector 106 allows for the first end of the movable connector 106 to maintain its connection with the top plate 102 and the second end to maintain its connection with the main housing 110 while allowing for movement in the z-direction of the top plate 102. This allows the thermal compliant cap 100 to be compliant with thermal expansion and compression of the electronic device 104.

Also note that the gap 136 has grown in size to accommodate the shift in the x-y direction of the electronic device 104. As a result, movable bar 126 has bent or otherwise morphed to accommodate the increase in the size of the orifice 136. The orifice 136 and the movable bar 126 allow for movement in the x-y direction of the top plate 102. This allows the thermal compliant cap 100 to be compliant with thermal expansion and compression of the electronic device 104 in an additional direction.

In an embodiment where the orifice 136 includes a low modulus seal material, the material would stretch to cover the elongated gap 136 to accommodate the increase in the size of the orifice 136. This would serve to further the purpose of the seal material, which is to seal the electronic device such that it is environmentally separated from the outside. Further, the seal material allows for stretch and movement in multiple directions such that the thermal compliant cap 100 is compliant with thermal expansion and compression of the electronic device.

In an embodiment of the present invention, the electronic device 104 is attached to the top plate 102 via a coupling element comprising a thermal paste or other adhesive (not shown). The coupling element may also include a heat spreader that allows the heat emanating form the electronic device 104 to spread and be transferred to the top plate 102 for dissipation.

FIG. 3 shows a top view of an alternative multi-dimensional compliant thermal cap 310, in one embodiment of the present invention. The thermal compliant cap 310 includes the equivalent structures of the thermal compliant cap 110, with the addition of supplementary movable connectors, movable bars and orifices in the main housing.

The compliant thermal cap 310 comprises a top plate 301 similar to top plate 102, comprising a flat rectangular plate that covers the top surface area of the electronic device that is not shown. A main housing 310 encircles and is coupled with the top plate 301. The main housing 110 extends downward and is placed on a substrate or an electronic circuit board.

The top plate 301 is attached to at least one of the movable connectors 302, 303, 304, 305, 306, 307, 308 and 309 that allow movement of the top plate 301 in the z-directions, or upwards and downwards. The movable connectors 302-309 are further connected to movable bars 322, 323, 324, 325, 326, 327, 328 and 329, respectively, that allow movement in the x-y direction, or sideways. Note that the movable bars 322-329 are integrated with the main housing 310 and the movable bars are formed from the establishment of slot orifices 332, 333, 334, 335, 336, 337, 338 and 339, respectively. That is, the fabrication of the slot orifices 332-339 create the movable bars 322-329 as an integrated element of main housing 310.

FIG. 3 also shows orifices 351-358. These orifices represent a gap between the top plate 301 and the main housing 310. The orifices 351-358 allow for the movement of the top plate 301 in any direction, including the x-direction and the x-y direction. In an embodiment of the present invention, the orifices 351-358, as well as slot orifices 332-339, are filled with low-modulus seal material such as silicone. The seal material fills each orifice and allows for stretch and movement in multiple directions such that the thermal compliant cap 300 is compliant with thermal expansion and compression of the electronic device.

The compliant thermal cap 300 serves the function of dissipating heat generated by the electronic device and conforms to thermal expansion of the device caused by the difference in the coefficients of thermal expansions of the materials of the device and the top plate 301 of the thermal compliant cap 300. Due to the movable nature of the connectors 302-309 and the bars 322-329, the complaint thermal cap 300 exhibits compliance in multiple directions, specifically, the “z” direction, as well as the “x-y’ directions, i.e., the up, down and sideways directions.

In an embodiment of the present invention, the thermal cap 300 (or thermal cap 100) is machined from a single element of a thermally conducting material, such as copper. The single element of thermally conducting material initially is machined, or drilled or cut, to include the features of present invention. In this embodiment, the top plate 301, as well as movable connectors 302, 303, 304, 305, 306, 307, 308 and 309 are created through the machining, or cutting, of orifices 351-358. Further, the movable bars 322, 323, 324, 325, 326, 327, 328 and 329, are created through the machining, or cutting, of slot orifices 332, 333, 334, 335, 336, 337, 338 and 339, respectively. That is, the fabrication of the slot orifices 332-339 create the movable bars 322-329 as an integrated element of main housing 310.

FIG. 4 shows a top view of an alternative multi-processor multi-dimensional compliant thermal cap 410, in one embodiment of the present invention. The thermal compliant cap 410 includes the equivalent of four cooling structures, as described in FIG. 3, aggregated to form one cooling structure that offers cooling and compliant functionalities to four separate electronic devices (not shown). Each quadrant of FIG. 4 (402, 404, 406 and 408) includes a cooling structure 100 and its corresponding components, as described with reference to FIG. 3.

The present invention can be utilized for cooling any of a variety of electronic devices. In one embodiment of the present invention, the present invention is used to cool a microprocessor of an information processing system such as a computer.

Therefore, while there has been described what is presently considered to be the preferred embodiments, it will be understood by those skilled in the art that other modifications can be made within the spirit of the invention. 

1. A cooling structure for an electronic device, the structure comprising: a compliant cap comprising a thermally conducting material disposed over the electronic device; wherein the compliant cap comprises a horizontal top surface and a horizontal support for the surface, the horizontal support comprising a compliant portion that allows the compliant cap to move in a z direction.
 2. The cooling structure of claim 1, wherein the horizontal top surface comprises a material having high thermal conductivity and the horizontal support comprises a material having compliant properties.
 3. The cooling structure of claim 1, further comprising a vertical structure coupled to the horizontal support, wherein the vertical structure holds the horizontal support and the horizontal top surface over the electronic device.
 4. The cooling structure of claim 1, wherein the cooling structure further comprises at least one fastener inserted through the substrate, the at least one fastener joining the electronic device and substrate when the electronic device is placed on the substrate.
 5. The cooling structure of claim 1, further comprising a coupling element disposed between the electronic device and the compliant cap.
 6. The cooling structure of claim 1, further comprising a spreader located over the electronic device and coupled with the compliant cap.
 7. A method of fabricating a cooling device, the method comprising: placing an electronic circuit on a substrate; and placing a compliant cap comprising a thermally conducting material over the electronic device; wherein the compliant cap comprises a horizontal top surface and at least one horizontal support for the surface, the horizontal support comprising a compliant bar that allows the compliant cap to move in multiple directions.
 8. The method of claim 7, further comprising including a coupling element between the electronic device and the compliant cap.
 9. The method of claim 8, further comprising applying a thermal paste between the electronic device and the compliant cap.
 10. The method of claim 9, further comprising applying a spreader over the electronic device for coupling with the compliant cap.
 11. The method of claim 7, further comprising inserting fasteners through the substrate for coupling with the electronic circuit.
 12. A method for fabricating a thermal cap for cooling an electronic device, the method comprising: machining a main housing of the thermal cap from a single sheet of a thermally conducting material; fabricating a top plate within the main housing by machining orifices around a perimeter of the main housing, the orifices forming a gap between the top plate and the main housing to allow movement of the top plate in x, y, and z directions; fabricating a moveable connector along an edge of the top plate by cutting a connector orifice in the main housing to allow movement of the top plate in the x direction; and fabricating a moveable bar coupled with the moveable connector by cutting a slot orifice in the main housing to allow movement of the top plate in the y and z directions.
 13. The method of claim 12 further comprising filling the connector orifice with a low-modulus seal material.
 14. The method of claim 13 further comprising filling the slot orifice with the low-modulus seal material.
 15. The method of claim 12 wherein the thermally conducting material comprises copper.
 16. A cooling structure for a plurality of electronic devices, the cooling structure comprising: a thermal compliant cap comprising a thermally conducting material disposed over the plurality of electronic devices; wherein the compliant cap comprises a horizontal top surface for each electronic device and at least one horizontal support for each of the horizontal top surfaces, wherein each horizontal support comprises a compliant portion that allows each compliant cap to move in multiple directions.
 17. The cooling structure of claim 16, wherein each horizontal support allows the corresponding horizontal top surface to in x, y, and z directions.
 18. The cooling structure of claim 16, wherein each horizontal top surface comprises a material having high thermal conductivity and each horizontal support comprises a material having compliant properties.
 19. The cooling structure of claim 17, further comprising a vertical structure coupled to the compliant cap, wherein the vertical structure holds each horizontal support and each horizontal top surface over the plurality of electronic devices.
 20. The cooling structure of claim 17, wherein the plurality of electronic devices are placed on a substrate and the cooling structure further comprises fasteners inserted through the substrate. 